It is known that fluorine-containing alkanes of 1 to 5 carbon atoms, such as chlorofluorocarbons (abbreviated as “CFCs”), hydrochlorofluorocarbons (abbreviated as “HCFCs”) and hydrofluorocarbons (abbreviated as “HFCs”), show volatility, stability and non-flammability. These fluorine-containing alkanes (also sometimes referred to as “Freons”) have thus been used as refrigerants, working fluids, foaming agents, sprays, cleaning agents, dissolving agents, solvents, etc. and made contributions to industrial developments. Further, these fluorine-containing alkanes have been widely used as blends of two or more kinds thereof. For example, there were commonly used mixed refrigerants R502, R507A, R404A, R407C and R401A according to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) standards. The above mixed refrigerants are each prepared by mixing two or more kinds of Freons at a specific ratio for improvements in coefficient of performance, refrigeration cycle, non-flammability, global warming potential and the like. Because of the volatility of the fluorine-containing alkanes, however, there occurs a composition change in the mixture by evaporation of any one of the Freons during use. The physical properties of the mixture vary due to such a composition change. It is thus preferable to form an azeotropic or azeotrope-like composition in that the vapor phase produced by volatilization has the same or substantially the same composition as does the liquid phase. The above-mentioned refrigerant R502 (that is, a mixed refrigerant of R22 and R115) and refrigerant R507A (that is, a mixed refrigerant of R143a and R125) are known as azeotropic refrigerants because each of these refrigerants is in the form of an azeotropic mixture having vapor and liquid phases of exactly the same composition. The above-mentioned refrigerant R410A is known as an azeotrope-like refrigerant because its constituent components R32 and R125 do not form an azeotropic mixture but form a mixture having vapor and liquid phases of substantially the same composition so that this mixture can be handled in practically the same manner as the azeotropic mixture. The applications other than the refrigerant applications include water removing agents each prepared by blending a fluorine-containing alkane with an alcohol, and cleaning agents each prepared by adding a non-flammable fluorine-containing alkane to a flammable hydrocarbon solvent so as to achieve non-flammability and controlled cleaning power. Even in these water removing/cleaning agent applications, as in the case of the refrigerant applications, it is preferable to form an azeotropic or azeotrope-like composition in that the vapor phase produced by volatilization has the same or substantially the same composition as does the liquid phase.
It is also known that the fluorine-containing alkanes as mentioned above are very stable in the air and long in atmospheric lifetime and become a cause of global warming. For these reasons, fluorine-containing olefins of 2 to 5 carbon atoms (such as hydrofluoroolefins, hydrochlorofluoroolefins, chlorofluoroolefins and fluoroolefins) have recently been proposed as substitutes for the above fluorine-containing alkanes. The fluorine-containing olefins, each of which has a double bond in the molecule, shows significantly high reactivity to OH radicals in the air as compared to the fluorine-containing alkanes with no double bond. The atmospheric lifetime of the fluorine-containing olefins is generally in days, whereas the atmospheric lifetime of the commonly used fluorine-containing alkanes such as HFC-365mfc, HFC-245fa and HFC-43-10 is in years. The fluorine-containing olefins, even if released into the air, get quickly decomposed and have less influence of global warming, ozone depletion etc. Further, it is reported that the fluorine-containing olefins have similar physical properties as those of the fluorine-containing alkanes and can be used for various applications such as refrigerants, working fluids, foaming agents, sprays, cleaning agents, dissolving agents, solvents, etc. The fluorine-containing olefins can be improved in performance by blending as in the case of the fluorine-containing alkanes. For example, Patent Document 1 teaches that: an azeotrope-like binary solvent system is formed by mixing of (Z)-1-chloro-3,3,3-trifluoropropene with 1,1,2,2-tetrafluoro-1-methoxyethane; and the thus-formed binary solvent has good cleaning effect on various oils. However, specific reports on azeotropic or azeotrope-like mixtures of fluorine-containing olefins are few in number as compared to those of fluorine-containing alkanes.
Patent Document 2 teaches a mixture of a fluorine-containing olefin of 3 carbon atoms and a general-purpose solvent and, in particular, discloses a degreasing test of 1,2-dichloro-3,3,3-trifluoropropene alone as Example 4. Patent Document 2 however gives no specific description about a mixture of 1,2-dichloro-3,3,3-trifluoropropene and flammable (E)-1,2-dichloro-ethylene (flash point: 2 to 4° C.) and its cleaning power, evaporation behavior, flammability or the like. Although 1,2-dichloro-3,3,3-trifluoropropene exists as geometric E- and Z-isomers that have intrinsic boiling points and polarities and thereby differ in drying property, cleaning power and polymer compatibility, Patent Document 2 gives no description about these geometric isomers. Patent Documents 3 to 7 teaches a resist remover, a buffing agent, an adhesive moisture removing solvent and a dry cleaning agent, but give no description about the geometric isomers of 1,2-dichloro-3,3,3-trifluoropropene and the detailed behavior of a blend of 1,2-dichloro-3,3,3-trifluoropropene and (E)-1,2-dichloro-ethylene as in the case of Patent Document 2.